Small-size engine-driven power generator apparatus have been known which include an engine for driving a power generator and a cooling fan connected to a drive shaft of the engine, and in which the engine and cooling fan are accommodated in a case and the case has an external air inlet port and a cooling air outlet port. One example of such small-size engine-driven power generator apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. HEI-11-200861 (JP H11-200861 A).
With the engine-driven power generator apparatus disclosed in JP H11-200861 A, operation of the cooling fan can introduce external air into the case through the external air inlet port so that the introduced external air is directed into a shroud of the engine as cooling air to cool the engine. The cooling air having cooled the engine is then sent from the shroud to the cooling air outlet port, through which it is discharged to outside the case.
Further, as the displacement of the engine increases, air suction and exhaust sound (or noise) increases. Thus, if the engine of the power generator apparatus is of a great displacement, it is necessary to provide a sound absorbing material on the inner surface of the case so as to suppress the air suction and exhaust sound of the engine.
However, providing the sound absorbing material on the inner surface of the case would increase the number of necessary component parts and thus increase the weight of the engine-driven power generator apparatus. Further, because providing the sound absorbing material on the inner surface of the case requires an extra space therefor within the case, the size of the engine-driven power generator apparatus would increase. Consequently, it has heretofore been difficult to reduce the weight and size of the engine-driven power generator apparatus. In addition, the increased weight and size of the engine-driven power generator apparatus would impair the mobility and portability of the engine-driven power generator apparatus.
Furthermore, with the engine-driven power generator apparatus disclosed in JP H11-200861 A, which is constructed to direct external air, introduced into the case, to the engine as cooling air to cool the engine, it was difficult to lower the temperature of the case by the cooling air flowing along the inner surface of the case.
Furthermore, in the engine-driven power generator apparatus disclosed in JP H11-200861 A, the entire engine, including its bottom portion, is surrounded by the shroud, so that the cooling air can be efficiently directed, via the shroud, to and along the bottom portion of the engine. Thus, the cooling air can cool the bottom portion of the engine to thereby efficiently cool the engine.
However, in order to direct the cooling air to and along the bottom portion of the engine, the engine-driven power generator apparatus disclosed in JP H11-200861 A necessitates the provision of the shroud surrounding the entire engine. Consequently, the shroud has to have a large size, which would increase the weight of the power generator apparatus. Further, the disclosed engine-driven power generator apparatus requires a large installation space for the shroud, which would increase the size of the power generator apparatus. Due to the increased weight and size, the mobility and portability of the disclosed engine-driven power generator apparatus would be impaired.
Another example of the engine-driven power generator apparatus is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2000-328957 (JP 2000-328957 A), where the cooling fan and power generator are connected to the drive shaft of the engine and covered with a metal cooling fan cover that is fixedly supported by the lower cover via mounting members. The engine-driven power generator apparatus disclosed in JP 2000-328957 A can efficiently direct the cooling air, sent from the cooling fan, to the engine by means of the cooling fan cover and cool the engine with the thus-directed cooling air.
However, with the engine-driven power generator apparatus disclosed in JP 2000-328957 A, where the cooling fan cover is fixedly supported by the lower cover via the mounting members, it is necessary to support the weights of the engine and power generator by the cooling fan cover. Thus, the cooling fan cover must have a high rigidity, and this is why the cooling fan cover is made of metal. But, because the metal cooling fan cover is relatively heavy in weight, it has heretofore been difficult to reduce the weight of the engine-driven power generator apparatus.